This invention relates to a fuel controller for an internal combustion engine which is equipped with a fuel injection system.
Generally, an internal combustion engine is equipped with an air flow sensor which is disposed upstream of the throttle valve and a crank angle sensor which is installed on the crankshaft of the engine. The amount of air which enters the engine between prescribed crankshaft angles is determined on the basis of the outputs of the air flow sensor and the crank angle sensor, and a fuel controller controls the amount of fuel which is supplied to the engine by fuel injectors in accordance with the amount of intake air and other operating parameters so as to attain a desired air-fuel ratio.
The timing with which fuel is supplied to the engine varies in accordance with the operating conditions. At a high engine rotational speed, the length of time for which each fuel injector is driven is increased, and the time at which fuel injection is started for each cylinder is advanced to an earlier portion of the engine operating cycle. For example, at low-speed operation, fuel injection generally starts during the power stroke of each cylinder, while at high speed operation, the start of fuel injection may be advanced into the compression stroke.
The amount of fuel which is to be supplied to the engine is calculated at prescribed time intervals regardless of the injecting timing, when the injection timing is advanced at high operational speeds, there may be a large time difference between the calculation of the amount of fuel to be supplied and the injection of the calculated amount of fuel. Accordingly, when the injection timing is advanced and thereafter, it becomes impossible to supply the necessary amount of fuel to the engine and a suitable air-fuel ratio ca not be obtained.